Process for limiting the excess force of an electrically controlled aggregate actuated by an external force when it nears its top or bottom stop positions, in particular for a motor vehicle window lifter nearing its closure position

ABSTRACT

A method for restricting the surplus force of an electrically controlled assembly operated by a foreign force, which can be used with particular advantage in connection with window lifters which are fitted with an anti-jam detection device. The method is characterized by a high automatic adaptation to the markedly fluctuating external conditions to which a window lifter is subjected, and by the compensation of system-conditioned fluctuations. The position of the assembly is continuously determined during the displacement process and at least one measured value correlated with the displacement force of the assembly is recorded in the inlet area of the stop position. This measured value is increased through the electronics unit by a predetermined amount and defined as a switch-off criterion so that the drive is switched off when this criterion is exceeded or understepped.

FIELD OF THE INVENTION

This invention relates to a method for restricting the surplus force ofan electrically controlled assembly operated by a foreign force uponcontact with an upper or a lower stop position, more particularly onhitting (or contacting) the closing position of a window lifter of amotor vehicle. The method is characterized by a high automaticadaptation to the markedly fluctuating external conditions, such as,temperature and dampness, to which the window lifter is subjected, aswell as the compensation of system-conditioned fluctuations, such asscattering of maximum engine torque of an electric motor.

BACKGROUND OF THE INVENTION

From DE 30 34 118 C2, a method is known for the electronic monitoring ofthe opening and closing process of electrically operated assemblies,such as for example window lifters and sliding roofs of motor vehicles,wherein characteristic values of the assembly are detected and evaluatedin a micro computer to ultimately generate setting signals for theelectric setting member of the assembly. The aim of this method is toavoid any dangerous jamming of parts of the body and objects, despitethe automatic opening and closing of a motor vehicle window. To thisend, the process of opening and closing the window is divided into threeareas. In order to allow a complete closing of the window pane it isnecessary to switch off the system for detecting a jammed state justbefore the upper edge of the pane could reach the sealing area,otherwise the window pane would reverse. The setting member is thus onlyswitched off when a sensor/electronics system has detected a blockingstate of the assembly for a predetermined time period.

With the electric motor being able to develop its maximum torque, thewindow pane is pressed into the seal with the maximum force available.Surplus forces reach a very high value because the drive has to bedesigned according to the most unfavorable conditions anticipated.Consequently, tensions arise in the door which can be the cause of windnoises and even untight or loose areas. Also, there is a danger ofincreased wear on the window lifter mechanism. Furthermore, a stabledesign of the mechanical loading parts leads to more expensive materialand greater weight.

SUMMARY OF THE INVENTION

The object of the invention is therefore to develop a method forrestricting the surplus force of an electrically controlled assemblyoperated by a foreign force on hitting or contacting an upper or a lowerstop position. More particularly, restricting the surplus force uponreaching the closing position of a window lifter of a motor vehiclewhich, through simple cost-effective means, prevents the occurrence ofunnecessarily high surplus forces and at the same time safely guaranteesreaching the stop position, more particularly the closing position, evenwhen the starting conditions, such as voltage of the energy source,large manufacturing tolerances of the adjustment system and climaticfactors, fluctuate quite considerably.

In the present invention, at least one measured value is detected in theinlet area of the stop position and is correlated with the displacementforce of the assembly. This measured value is increased through theelectronics unit by a predetermined amount (for example relative amountor amount calculated through a functional connection) and is defined asthe switch-off criterion so that when this criterion is exceeded orunderstepped the drive is switched off.

The inlet area is regarded as the displacement area of the assemblywhich either begins just before reaching the stop position and endsafter a following displacement path, or which only begins on reachingthe stop position and ends after a further displacement path whichcauses an elastic deformation of at least a part of the displacementsystem. The most advantageous design can only be determined when takinginto consideration the concrete conditions of each individual case.Determining the amount, more particularly the relative amount, by whichthe measured value is to be increased for safely reaching the stopposition, is best carried out empirically.

In relation to a window pane of a motor vehicle, a characteristic fieldof measured values is recorded with the variation of the most importantmeasuring factors acting on the movement of the window pane during theclosing process and on hitting the lower stop position of the windowpane. Such influencing factors are inter alia temperature, dampness, iceand some geometric tolerances which are important for the movement ofthe pane. From this characteristic field the case should then beselected where the torque requirement to be expected for safely hittingthe stop position, more particularly the closing of the window pane,compared with the available torque of the motor, is used up to thegreatest possible extent. From the measured values (e.g. electriccurrent, the moment, the period length of the electric motor) correlatedwith these two torque values, it is possible to obtain a factor forgenerating the switch-off criterion. If the factor thus obtained forgenerating the switch-off criterion is then constantly applied to thatin the inlet area of the upper and lower stop position, then the windowpane is always completely closed and completely opened, respectively.

Naturally, it is possible to obtain a higher degree of adapting themethod to the relevant prevailing conditions if the characteristicfield, set up by measurements, is provided in the form of a table ofvalues or even in the form of mathematically functional connections inthe micro electronics unit.

According to a further variation of the invention, it is proposed togenerate the switch-off criterion on the basis of a measured valuecorrelated with: the displacement force before the first contact betweenthe seal and the upper edge of the pane, and a measured value of thedisplacement force which was detected immediately after the upper edgeof the pane entered into the seal.

The sealing area should thereby be no more than 50%. The measured valuefor the closing area is 25% to 50% of the depth of an inner displacementpath of the sealing area in front of the seal. In each case it is to beensured that the signal evaluation and generation of the switch-offcriterion takes place sufficiently quickly. The advantage of thevariation just described is that both the sliding properties of thewindow pane and the sealing properties are included in the calculation.

If crossing through the sealing area offers sufficient time for severalmeasurements inside the seals, then the changing conditions inside theseal can also be measured and considered.

Advantageously, the invention can be used also for electricallycontrolled window lifters with anti-jam detection because all thepre-requisites for signal detection and signal evaluation are alreadyprovided here. When using an electromotor drive, it is readily possible,for example by means of an echo sensor, to use the period length as acorrelation value for the displacement force because the motorcharacteristic field has a clear connection between the speed andtorque. Likewise measured values of the electric current could be usedfor this purpose.

The method can also be used for hitting or contacting the lower stop ina similar way to the variation of the invention just described forclosing the window pane. To this end, means are provided which contactthe window pane just before the stop position is reached and cause areduction in the motor speed and thus an increase in the period length.Such means for producing local slow motions can be readily formed asspring elements or elastic damping elements. For elastic dampingelements, the inlet area only begins with contact of the damping elementand ends after a further displacement path of the displacement system,which causes an elastic deformation of the damping element.

At this point it should be pointed out that the inherent elasticity ofseveral displacement systems, more particularly arm window lifters, isso great that no additional damping elements need be used for hittingthe stop positions. The inlet area hereby starts on reaching the stopand ends after a further displacement path of the displacement systemwhich causes an elastic deformation of the displacement system.

Through this method, it is ensured that the conditions prevailingoverall are taken into consideration each time on hitting or uponcontacting the stop positions so that the displacement force is providedin just the sufficient amount. Undesired surplus forces are herebyminimized.

In view of the possibility of differences occurring, considerably morethan 100% relative to the available displacement force when comparingtwo displacement systems of the same type, obviously the surplus forcerestriction also provides possibilities for structural improvements,which can be directed to saving weight for example.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be explained in further detail with reference toan embodiment of a window lifter and the drawings in which:

FIG. 1 is a sectional view of a window pane of a motor vehicle with aseal for the upper edge of the pane;

FIG. 2 is a diagrammatic illustration showing the change in the forceacting on the window pane versus position;

FIG. 3 is a sectional view of a window pane of a motor vehicle with aguide rail and a lower stop with a friction element mounted at the side;and

FIG. 4 is a sectional view of a window pane of a motor vehicle with aguide rail and a lower stop of elastic material with relatively large(elastic) deformability.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The diagrammatic illustration of FIG. 1 shows in particular the partsrelating to the sealing area/closing area 3 and the seal inlet area 4.The window pane 1 is located with its closing edge 1 a directly at thestart of the sealing area 3 but without having already contacted theseal 2. The seal inlet area 4, in which at least one measured value isdetected correlating with the displacement force of the window pane,starts roughly at a distance from the seal 2 corresponding to about 25%to 50% of the extension of the sealing area 3, and ends level with themechanical stop 20.

The positions of the assembly during a displacement process and in aninlet area (4, 4′, 4″) of the stop position (20, 7, 7′) are continuouslydetected by technical measuring means. At least one measured valuecorrelated with a displacement force of the assembly is recorded. Themeasured value is increased through an electronics unit by apredetermined amount and is defined as the switch-off criterion so thata drive is switched off when this criterion is exceeded or understepped.

When the closing edge 1 a of the window pane 1 reaches the inner stop 20of the seal 2, the closing process is basically regarded as finished.However, it is advantageous to operate the electromotor drive just alittle more to slightly tension the displacement system. This providesextra security for correctly and permanently reaching the controlledstop position. As a result, acceleration along the displacement axisdoes not lead to relative movements of the displacement object nor thenoises connected therewith. Unnecessarily large tensions in the systemare avoided by a determination of the suitable switch-off criterion andthe amount required to turn off the system.

An embodiment of the invention will now be explained in further detailwith reference to the diagrammatic illustration of FIG. 2. The periodlength T (in milliseconds) of the drive shaft and displacement force F(in Newton) are entered respectively on the abscissa. The ordinateindicates the position of the window pane 1 between the fully openedstate (OPEN) and the fully closed state (CLOSED) in front of which thesealing area 3 extends.

The illustrated curve shows the principle course of the displacementforce F and the period length T during the displacement process of thewindow pane 1. In general the displacement forces rise slightly as aresult of slightly increasing friction in the side guide elements whichleads to a corresponding reduction in the motor speed and thus to anincrease in the period length T.

According to the present embodiment the period length for reaching thesealing area 3 at point 10 amounts to 50 ms. This measured value servesas a basis for generating the switch-off criterion in which the measuredvalue is increased by a certain amount. The increase can however takeplace according to one of the methods already described in the summary,for example, through multiplication with a factor from a table of valueswhich is provided in a micro computer. In this case the increase factorhas the value 1.7. Thus the value for the switch-off criterion isproduced as 50 ms×1.7=85 ms. The drive is switched off as soon as thesensor/electronics system detects a period time T which exceeds 85 ms.

At point 11 the closing edge of the window pane 1 reaches the stop 20 ofthe seal 2 with a displacement force F1. Since at this point 11 theperiod length with T=70 ms still lies below the switch-off criterion ofT=85 ms, there is now a force build up until F=FU. The surplus forcewhich is produced from the difference, FU−F1, remains very small becausethe drive is stopped just shortly after reaching the closing position.

Without the surplus force restriction according to the invention, themotor would increase the displacement force F up to the point 13 with aforce FUU if it is assumed that the motor has reached its maximum torqueat this point 13. The surplus force is produced from the differenceFUU−F1, which amounts to a multiple of the surplus force restrictedaccording to the invention.

In addition to hitting or contacting the described closing position, themethod is also suitable for hitting or contacting the position of theassembly (e.g. window lifter, sliding roof) in which the largestpossible opening is reached. This happens on reaching the lower stopposition.

FIG. 3 shows in a heavily simplified diagrammatic illustration a sectionthrough a guide rail 5 of a cable window lifter along which a windowpane 1 is displaced. An angular deflection of the guide rail 5 forms thestop 50 which is associated with a friction element in the form of aspring 6 and an elastic damping element 7, made, for example, of rubber.Upon hitting the lower stop 50, the lower edge 1 b first strikes thespring 6 which is mounted in front of the stop 5. The stop 5 is alignedaccording to the displacement axis 100, and is located in front of thedamping element 7 which is supported on the side arm of the guide rail5.

The inlet area 4′, analogous to the inlet area 4 according to FIG. 1(for hitting the closing position of a window pane), is defined for theembodiment of FIG. 3 so that it starts with the first contact of thelower edge 1 b of the pane with the spring 6 and ends with the contactof the damping element 7. The spring 6 causes a sudden and easily sensedslow motion of the window pane 1. Naturally the inlet area 41 can alsobe extended somewhat further upwards so that its start lies above thespring 6 and information from this displacement area can be used forgoverning the lower stop position.

The choice of a large inlet area 4′ is particularly advantageous if acomparatively long displacement path has to be covered for generating ameasuring signal for generating the switch-off criterion and/or afterthe switch-off command for the drive, it is anticipated that theassembly will run on so far that a sufficient restriction of the surplusforce can no longer be safely guaranteed.

FIG. 4 shows an embodiment which is slightly modified compared with FIG.3 and which has a very small inlet area 4″. The inlet area 4″ is formedby a deformation zone of the elastic damping element whereby thenon-deformed state of the damping element is marked 7′ and the deformedstate of the damping element is marked 7′. Short inlet areas 4″ of thiskind can be used without a problem if a comparatively dense signalsequence is generated on the displacement path and/or a high inherentelasticity of the displacement system is present.

The measured value of the correlation factor can correspond to ameasured value which was determined after the assembly strikes theelastic stop 7, 7′.

At this point it should be pointed out that the springs and dampingelements described can also be fixed in the area of the lower edge 1 bof the pane or mounted on an entrainment member (not shown) for thewindow pane 1.

What is claimed is:
 1. A method for restricting surplus force of anelectronically controlled window lifter upon contacting at least onestop position whereby an upper edge of a window pane reaches a stop of aseal, the method comprising: continuously detecting positions of thepane during a displacement process; recording at least one measuredvalue correlated with a displacement force of the pane after entrance ofan upper edge of the pane into at least about 25% of a depth of an innerdisplacement path of a sealing area of the seal; and increasing themeasured value through an electronics unit by a predetermined amount todefine a switch-off criterion so that a drive of the window lifter isswitched off when this criterion is one of exceeded and understepped. 2.The method according to claim 1 further comprising determining the stopposition.
 3. The method according to claim 1 wherein the measured valuecorrelated with the displacement force of the pane is one of an electriccurrent, a moment and a period length of a drive shaft of an electricmotor.
 4. The method according to claim 1 further comprising determiningthe increased amount as a percentage value on the basis of thepreviously measured value correlated with the displacement force of thepane.
 5. The method according to claim 1 wherein the measured valuecorrelated with the displacement force of the pane corresponds to themeasured value immediately prior to the pane striking the stop.
 6. Themethod according to claim 5 further comprising determining the measuredvalue for the sealing area of the displaceable window pane when the paneis in an area which is 25% to 50% of a depth of an inner displacementpath of the sealing area in front of the seal.
 7. The method accordingto claim 1 wherein the measured value correlated with the displacementforce of the pane is determined after the upper edge of the pane hascovered at most half of a displacement path lying in the sealing area.8. The method according to claim 1 further comprising: recording ameasured value correlated with a displacement force of the assemblydirectly in front of the seal; and generating the switch-off criterionby using a ratio of the value measured directly in front of the seal andthe value measured after the upper edge of the pane enters into theseal.
 9. The method according to claim 8 wherein the ratio of the twomeasured values for generating the switch-off criterion is related tothe measured value recorded directly in front of the seal.
 10. Themethod according to claim 8 wherein the ratio of the two measured valuesfor generating the switch-off criterion is related to the measured valuerecorded after the inlet of the upper edge of the pane.
 11. The methodaccording to claim 1 wherein the measured value correlated with thedisplacement force of the pane corresponds to a measured valuecorrelated with the displacement force of the pane which is determinedafter the pane strikes an elastic stop.
 12. The method according toclaim 1 further comprising generating the switch-off criterion on thebasis of at least two measured values correlated with the displacementforce of the pane recorded after the upper edge of the pane has enteredinto the sealing area.
 13. A device for restricting surplus force of anelectronically controlled window pane operated by a foreign force of amotor vehicle upon contacting at least one stop position, wherein anupper edge of the window pane reaches a stop of a seal, the devicecomprising: a position detector that continuously detects the positionof the pane in at least one of during displacement of the pane and in aninlet area of the stop position; a recorder that records at least onemeasured value correlated with a displacement force of the pane afterentrance of an upper edge of the pane into at least about 25% of a depthof an inner displacement path of a sealing area of the seal; and aswitch-off criterion determined by one of increasing and decreasing themeasured value through an electronics unit by a predetermined amount,wherein a drive is switched off and the window pane stops inside of thesealing area when this criterion is one of exceeded and understepped,respectively.
 14. The device of claim 13 further comprising a frictionelement which increases the slow motion of the window pane beforereaching the stop position.
 15. A method for restricting surplus forceof an electronically controlled window lifter upon contacting at leastone stop position in a sealing area of a seal, the method comprising:continuously detecting positions of a window pane during a displacementprocess; recording a measured value correlated with a displacement forceof the pane after entrance of an upper edge of the pane into at leastabout 25% of a depth of an inner displacement path of the sealing areaof the seal; and increasing the measured value through an electronicsunit by a predetermined amount to define a switch-off criterion suchthat a drive of the window lifter is switched off and the window panestops inside of the sealing area when this criterion is one of exceededand understepped.
 16. The method of claim 1 wherein the at least onemeasured value correlated with a displacement force of the pane isrecorded when the upper edge is at about 25% of the depth of the innerdisplacement path of the sealing area of the seal.
 17. The deviceaccording to claim 14 wherein the friction element is formed as aspring.